Delay the test execution to avoid flakiness

The frame's initialization code focuses the content from browser
process via an IPC (browser->renderer), but its handling in the
renderer can be delayed until after the test code script execution
is started.

This caused the test to have a race condition, that a focus event
is delivered where it is not expected, and resulted the flakiness.
The test can fail on the initial use of content_shell process.

Delay the execution of test function so that it will not be
affected by the frame initial focus event.

Bug: 863067
Change-Id: I475d912b0e9baffa3917212b2fc0735189381cb8
Reviewed-on: https://chromium-review.googlesource.com/1146523
Commit-Queue: Takayoshi Kochi <kochi@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577124}
2 files changed